Buggy code:
private static final short RFLAG_ENABLED_IN_HIERARCHY_VALUE = 1 ; private static final short RFLAG_ENABLED_IN_HIERARCHY_SET = 2 ; private static final short RFLAG_VISIBLE_IN_HIEARARCHY_VALUE = 4 ; private static final short RFLAG_VISIBLE_IN_HIERARCHY_SET = 8 ; private static final short RFLAG_CONFIGURED = 16 ; private static final short RFLAG_BEFORE_RENDER_SUPER_CALL_VERIFIED = 32 ; private static final short RFLAG_INITIALIZE_SUPER_CALL_VERIFIED = 64 ; private transient short requestFlags = 0 ; private String id ; private MarkupContainer parent ; int generatedMarkupId = - 1 ; private transient IMarkupFragment markup ; Object data = null ; final int data_start ( ) { } final int data_length ( ) { } final Object data_get ( int index ) { } final void data_set ( int index , Object object ) { } final void data_add ( Object object ) { } final void data_insert ( int position , Object object ) { } final void data_remove ( int position ) { } public Component ( final String id ) { } public Component ( final String id , final IModel < ? > model ) { } public IMarkupFragment getMarkup ( ) { } final boolean internalOnMarkupAttached ( ) { } protected void onMarkupAttached ( ) { } private boolean moveComponentToItsRealParent ( ) { } public final String getMarkupIdFromMarkup ( ) { } public final void setMarkup ( final IMarkupFragment markup ) { } protected void onConfigure ( ) { } protected void onInitialize ( ) { } final boolean isInitialized ( ) { } void initialize ( ) { } final void fireInitialize ( ) { } public final void afterRender ( ) { } private final void internalBeforeRender ( ) { } private static final MetaDataKey < List < Component > > FEEDBACK_LIST = new MetaDataKey < List < Component > > ( ) { private static final long serialVersionUID = 1L ; } ; public final void beforeRender ( ) { } public final void configure ( ) { } public final boolean continueToOriginalDestination ( ) { } public final void debug ( final Serializable message ) { } final void internalOnRemove ( ) { } public final void detach ( ) { } public void detachModels ( ) { } public final void error ( final Serializable message ) { } public final void fatal ( final Serializable message ) { } public final < Z > Z findParent ( final Class < Z > c ) { } public final MarkupContainer findParentWithAssociatedMarkup ( ) { } public final Application getApplication ( ) { } public final String getClassRelativePath ( ) { } public < C > IConverter < C > getConverter ( Class < C > type ) { } public final boolean getEscapeModelStrings ( ) { } public final FeedbackMessage getFeedbackMessage ( ) { } public String getId ( ) { } public final IModel < ? > getInnermostModel ( ) { } public Locale getLocale ( ) { } public final Localizer getLocalizer ( ) { } private final ComponentTag getMarkupTag ( ) { } public final ValueMap getMarkupAttributes ( ) { } public final Object getMarkupIdImpl ( ) { } private final int nextAutoIndex ( ) { } public String getMarkupId ( boolean createIfDoesNotExist ) { } public String getMarkupId ( ) { } public final < M extends Serializable > M getMetaData ( final MetaDataKey < M > key ) { } private MetaDataEntry < ? > [ ] getMetaData ( ) { } public final IModel < ? > getDefaultModel ( ) { } public final Object getDefaultModelObject ( ) { } public final String getDefaultModelObjectAsString ( ) { } public final String getDefaultModelObjectAsString ( final Object modelObject ) { if ( modelObject != null ) { final Class < ? > objectClass = modelObject . getClass ( ) ; final IConverter converter = getConverter ( objectClass ) ; final String modelString = converter . convertToString ( modelObject , getLocale ( ) ) ; if ( modelString != null ) { if ( getFlag ( Component . FLAG_ESCAPE_MODEL_STRINGS ) ) { <START_BUG> return Strings . escapeMarkup ( modelString , false , true ) . toString ( ) ; <END_BUG> } return modelString ; } } return "" ; } public final boolean getOutputMarkupId ( ) { } public final boolean getOutputMarkupPlaceholderTag ( ) { } public final Page getPage ( ) { } public final String getPageRelativePath ( ) { } public final MarkupContainer getParent ( ) { } public final String getPath ( ) { } public final boolean getRenderBodyOnly ( ) { } public final Request getRequest ( ) { } public final RequestCycle getRequestCycle ( ) { } public final Response getResponse ( ) { } public Session getSession ( ) { } public long getSizeInBytes ( ) { } public final String getString ( final String key ) { } public final String getString ( final String key , final IModel < ? > model ) { } public final String getString ( final String key , final IModel < ? > model , final String defaultValue ) { } public final String getStyle ( ) { } public String getVariation ( ) { } public final boolean hasBeenRendered ( ) { } public final boolean hasErrorMessage ( ) { } public final boolean hasFeedbackMessage ( ) { } public final void info ( final Serializable message ) { } public final boolean isActionAuthorized ( Action action ) { } public final boolean isEnableAllowed ( ) { } public boolean isEnabled ( ) { } public final boolean isRenderAllowed ( ) { } public final boolean isStateless ( ) { } public boolean isVersioned ( ) { } public boolean isVisible ( ) { } public final boolean isVisibleInHierarchy ( ) { } public final void markRendering ( boolean setRenderingFlag ) { }

Fix:
return Strings . escapeMarkup ( modelString , false , false ) . toString ( ) ;